Although earth orbiting communication satellites have been in use for a number of years, the problem of providing adequate cooling for the vital and thermally sensitive electronic components of such satellites has continued to plague designers. Heat resulting from solar radiation can be reflected away from the satellite by providing those portions of its exterior not covered with solar cells and other equipment such as antennas with a suitable reflecting surface. However, the electronics carried within the satellite generate their own heat which somehow must be rejected from the satellite in order to maintain the temperatures of the electronics within safe operational limits and thereby to prolong their life.
One known technique for removing heat from such a satellite is to position the relatively hot electronics elements in packages or compartments located near the periphery of the satellite and to locate a mirror radiator outboard of the electronics to absorb heat radiated by the electronics and re-radiate this heat to the environment of the satellite. One such prior art mirror radiator comprises an exterior layer of quartz which is silvered on the interior side and backed by an aluminum honeycomb which is blackened on its interior side. Such a mirror radiator absorbs heat from its interior side and re-radiates it to the environment of the satellite but also tends to reflect heat reaching the satellite from its environment.
Unfortunately, the thermal absorptance, reflectance and transmittance of the mirror radiator change irreversibly with time so that over the life of the satellite, less and less of the heat generated by the satellite electronics can be rejected through such a mirror radiator. In addition, such a mirror radiator can re-radiate only heat which flows to it radially from the electronics of the satellite. This means, in effect, that most heat radiated axially by the electronics misses the mirror reflector and is absorbed by the interior structure of the satellite. Although such axially radiated heat could, to some extent, be captured by a mirror radiator which is considerably longer than the electronics compartments, such a solution is not optimum since it would result in a loss of satellite surface for photocells, would be expensive due to the high cost of such mirror radiators and would result in a more bulky structure. A need has existed over a number of years for a simple, effective means for absorbing and re-radiating such axially radiated heat without requiring the use of greatly enlarged mirror radiators.